Questions tagged [diaphragm]

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3 answers
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Understanding Entrance Pupil

let's consider a simple lens without diaphragm. For a lens like this, the book Science for Curious Photographer states that: The important fact is that the illumination of the image is proportional ...
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1 vote
1 answer
82 views

Should the iris of a Canonet QL17 contract at all in AE mode at maximum aperture?

Note that you need to cock the shutter for the tests below, otherwise the iris doesn't fully engage with the aperture controls. If I set my QL17 to ƒ/1.7, the iris opens up fully (as I'd expect) If I ...
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5 answers
600 views

EOS 250D the aperture changing only when picture is taken

I have yongnuo 50mm f1.8 lens In Av Mode When I m changing the fstop the diaphragm blades remains fully open and depth of field doesn't change I have looked to user Guide and find that I can assign ...
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-1 votes
3 answers
139 views

Real light increments using aperture scale in fractional stops

In the case of using f-number with full stops, the +1EV step means 2*light because the Area (A = πr^2) in the diaphragm is doubled (i.e. radius*√2). However, I don't know why in fractional stops such ...
  • 113
0 votes
3 answers
116 views

What techniques do higher-end lenses use to reduce astigmatism at high apertures?

I own a few lenses with a maximum aperture of f/2.8. For this question, I'll focus on two specifically: A Rokinon 14mm f/2.8, which retails around the $500 CAD mark; and A Sigma 24-70 f/2.8, which ...
0 votes
1 answer
199 views

How is the diameter of a non-circular (effective) aperture actually measured?

An f-number is determined as the ratio of the focal length to the diameter of the entrance pupil. But the actual aperture diaphragm is usually not a perfect circle. Its shape is determined by the ...
  • 901
0 votes
1 answer
176 views

Canon 24-105mm aperture diaphragm screw size

I need to mount a Canon 24-105mm aperture diaphragm unit to something, but I don't have any screws for it. In the lens itself, it is attached to some sort of mount via 3 screws that screw into the ...
  • 113
0 votes
3 answers
85 views

Is there a difference in image when using a two different combinations of exposure time and diaphragm? [duplicate]

My camera, aimed at a motionless object, is mounted on a tripod. Do I get a different image by changing exposure time and the diaphragm in such a way that the total amount of light coming in stays the ...
1 vote
2 answers
136 views

Is there a datasheet for the Canon 24-105mm diaphragm unit?

Does anyone know if a datasheet is available for the Canon 24-105mm diaphragm unit? I'm wondering if there's a way to use an Arduino or suchlike to control the diaphragm via the flex cable, but I can'...
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3 votes
1 answer
5k views

What is an electromagnetic diaphragm?

What is an electromagnetic diaphragm, how it works, and how is it different with regular diaphragms? A specialized electromagnetic diaphragm mechanism operates in precise sync with the camera's ...
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